The use of wavelength-selective reflectors is known for the selection and/or stabilisation of an emission wavelength of a laser. Such reflectors can delimit an optical resonator of the laser at one end of the resonator and for example be designed as Bragg reflectors, also called DBR (distributed Bragg reflectors). Such lasers are therefore indicated as DBR lasers. Bragg reflectors normally comprise a multitude of dielectric layers with an alternating refractive index, wherein a reflection spectrum of the Bragg reflector is determined by a thickness and by refractive indices of the dielectric layers. The reflectivity of the Bragg reflector has a maximum when a wavelength of the incident light is equal to the multiple of an optical path length of an individual one of the layers of the reflector.
The wavelength of the reflection maximum of a Bragg reflector can be changeable for example by way of changing the temperature or by way of applying an electrical field, and a change of an effective refractive index which this entails. An emission wavelength of DBR lasers known from the state of the art, on account of this, can be tuned within a wavelength region which typically however is very restricted. A laser, with which a wavelength-selective element is designed as a Bragg reflector and with which a refractive index of a material of the Bragg reflector can be changed, is disclosed for example in the document EP 2 169 788 A1. A rapid setting between different emission wavelengths with such a laser is however only possible to a limited extent due to the necessary temperature stabilisation of the reflector. Moreover, it would be advantageous if the wavelength region, within which the emission wavelength of the laser is changeable, could be increased.